In the electronics industry, printed circuit boards are often interconnected in card cages or mainframes that include mounting hardware and electrical connections for receiving the printed circuit boards. A typical system is a VXI mainframe and corresponding printed circuit (PC) board modules, which have been standardized by the VXIbus Consortium, Inc. for interchangeability among different vendors. Generally, the printed circuit boards are housed in modules which slide in and out of all vendor's mainframes with the electrical connections between the various modules being made by electrical plug-in connectors at the back of the printed circuit boards and corresponding electrical connectors at the back of the mainframe.
This type of electrical connection between the printed circuit board module and the 20 mainframe is more fully described in related U.S. patent application Ser. No. 08/369,070, filed Jan. 5, 1995 to Arnold Joslin, entitled IMPROVED INJECT-EJECT SYSTEM FOR RACK MOUNTED PLUG-IN MODULES, which is hereby incorporated by reference for all that it teaches. Generally, several modules (approximately 6-13) are inserted side-by-side into a mainframe with relatively little space between the individual modules (approximately 0.012 inches). Typically, if the PC module is to be utilized with external devices, a connector or terminal block is connected to electrical pin connectors at the front end of the PC module.
FIG. 1 shows a printed circuit module 100 with two electrical connectors 110 that include male connector pins 112. There are also similar connectors 111 at the back of module 100, which are used to connect module 100 to a mainframe (not shown). Also shown is a typical connector or terminal block 102, which is used to connect the inputs and outputs (I/O) of module 100 to external devices, such as devices under test. Terminal block 102 has two electrical connectors 114, which include female connector holes (not shown) that mate with to the male connector pins 112 of connectors 110. Terminal block 102 further includes a printed circuit board 104 (shown disengaged from terminal block 102) with connectors 106 that permit interconnection between connectors 114 and external wiring, which is routed through cable routing aperture 108 to devices under test.
Terminal block 102 is typically connected to module 100 by an operator applying physical force to the back wall 118 of terminal block housing 102 until connectors 114 and 112 are mated. Terminal block 102 is then secured to module 100 by means of small screws used to secure attachment member 116 to attachment block 120. External connection wires (not shown) are connected to printed circuit board 104 (inside terminal block housing 102) and then routed through cable routing aperture 108. Terminal block housing 102 is typically made of a hard plastic material.
The current trend in the industry is to increase the I/O signal count from module 100 to the device under test, which means that the connectors 112 and 114 can now have between 96 and 320 or more connector pins. This corresponds to an insertion and removal force of approximately 24 to 75 or more pounds. As terminal block 102 does not have alignment guides for mating with the printed circuit module, the connector pins 112 of connectors 110 and the corresponding holes in connectors 114 are used as alignment guides, which may cause many connector pins 112 to be damaged. A similar problem with terminal blocks of the prior art is that there is no way to insure that the force applied by the operator is applied in a uniform manner, so that there is no angular misalignment between connectors 114 or 106 in the terminal housing 102 and connectors 110 in module 100. Furthermore, the plastic housing of terminal block 102 is frequently damaged due to operators applying upwards of 75 pounds of force to the back wall 118 in order to connect terminal block 102 to module 100.
It should also be noted that most mainframe card cages are mounted on wheels. This fact in combination with the 24 to 75 pounds of insertion and extraction force applied to the front of the module can result in the mainframe being pushed across the floor or may require more than one operator to insert or extract the terminal block from the module--one to push on the terminal block at the front of the mainframe and one to secure the mainframe against movement.
Another dilemma caused by the increase in I/O's is routing 96 to 320 or more wires through the small cable routing aperture 108. The routing of too many wires through cable routing aperture 108 causes excessive stress on the plastic housing of terminal block 102, which can result in the cracking or breaking of the housing. Also, routing too many wires through cable routing aperture 108 may cause the sides of the housing of terminal block 102 to bend outward, potentially interfere with neighboring modules and terminal blocks in the mainframe (not shown). It is not feasible to increase the size of cable routing aperture 108 and maintain the structural rigidity necessary for the terminal block housing 102. It is also not feasible to route wire through top and bottom walls 122 of terminal block 102 with the current configuration of typical terminal blocks, as the attachment of attachment member 116 to attachment block 120 requires a tool, such as a screw driver, to secure the attachment of terminal block 102 to module 100 in the area that wires would exit from terminal block along the top and bottom walls 122. It is further not feasible to route wire through the sides of the terminal block housing, as this would interfere with immediate neighboring modules and terminal blocks.
A further problem with the prior art terminal block 102 is that an operator may inadvertently insert, or attempt to insert, the terminal block into the printed circuit board module 100 upside down. This may result in the connector pins 112 being bent or broken. Worse yet, if the terminal block is successfully inserted upside down, the electronics of the device under test, the module or the mainframe may be damaged.
Accordingly, it would be a substantial improvement in the field to provide a termination block for signals from electronic systems such as VXI modules to devices under test that overcomes the disadvantages of existing systems, such as the application of misaligned force to connector pins during the insertion process, the application of excessive force to the terminal block housing during the insertion process, the bending outward or breaking of the terminal block housing due to routing too many wires through a single cable routing aperture. It would be a further advantage to provide a terminal block that has easier insertion, attachment and removal processes than the terminal blocks of the prior art. It would be yet a further advantage to provide a terminal block that cannot be inserted into a printed circuit board module in an inverted position.